fix: guard localStorage quota writes

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- **PR #2387** by @Michaelyklam (closes #2386) — Active-session and workspace-panel `localStorage` writes now degrade gracefully when browser storage quota is exhausted. The missed session/panel persistence writes now match the existing best-effort storage pattern so clicking sessions, creating chats, completing streams, and toggling the workspace panel no longer throw uncaught `QuotaExceededError` exceptions.
+
 ## [v0.51.74] — 2026-05-16 — Release AX (stage-367 — 4-PR safe-lane batch — #2362 table-cell spacing + #2363 run-state-consistency RFC + #2365 custom_providers list-format + #2367 settings sidebar i18n)
 
 ### Added

static/boot.js

@@ -101,7 +101,7 @@ function _setWorkspacePanelMode(mode){
   // Persist open/closed across refreshes (browse/preview → open; closed → closed)
   // Do NOT overwrite the user's "keep open" preference — only track runtime state
   // so that toggleWorkspacePanel(false) from the toolbar doesn't clear the setting.
-  localStorage.setItem('hermes-webui-workspace-panel', open ? 'open' : 'closed');
+  try{localStorage.setItem('hermes-webui-workspace-panel', open ? 'open' : 'closed');}catch(_){}
   layout.classList.toggle('workspace-panel-collapsed',!open);
   if(_isCompactWorkspaceViewport()){
     panel.classList.toggle('mobile-open',open);

static/commands.js

@@ -424,7 +424,7 @@ async function _applyManualCompressionResult(data, focusTopic, visibleCount, com
       S.messages=data.session.messages||[];
       S.toolCalls=data.session.tool_calls||[];
       clearLiveToolCards();
-      localStorage.setItem('hermes-webui-session',S.session.session_id);
+      try{localStorage.setItem('hermes-webui-session',S.session.session_id);}catch(_){}
       if(typeof _setActiveSessionUrl==='function') _setActiveSessionUrl(S.session.session_id);
       syncTopbar();
       renderMessages();

static/messages.js

@@ -1454,7 +1454,7 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
           const _prevCost=(S.session&&S.session.estimated_cost)||0;
           S.session=d.session;S.messages=d.session.messages||[];if(typeof _messagesTruncated!=='undefined')_messagesTruncated=!!d.session._messages_truncated;
           if(S.session&&S.session.session_id){
-            localStorage.setItem('hermes-webui-session',S.session.session_id);
+            try{localStorage.setItem('hermes-webui-session',S.session.session_id);}catch(_){}
             if(typeof _setActiveSessionUrl==='function') _setActiveSessionUrl(S.session.session_id);
           }
           const _markerOnlyAssistantError=_replaceMarkerOnlyAssistantWithStreamError(S.messages);
@@ -1824,7 +1824,7 @@ function attachLiveStream(activeSid, streamId, uploaded=[], options={}){
         clearLiveToolCards();if(!assistantText)removeThinking();
         S.session=session;S.messages=(session.messages||[]).filter(m=>m&&m.role);
         if(S.session&&S.session.session_id){
-          localStorage.setItem('hermes-webui-session',S.session.session_id);
+          try{localStorage.setItem('hermes-webui-session',S.session.session_id);}catch(_){}
           if(typeof _setActiveSessionUrl==='function') _setActiveSessionUrl(S.session.session_id);
         }
         const _markerOnlyAssistantError=_replaceMarkerOnlyAssistantWithStreamError(S.messages);

static/sessions.js

@@ -416,7 +416,7 @@ async function newSession(flash, options={}){
   S.session=data.session;S.messages=data.session.messages||[];
   S.lastUsage={...(data.session.last_usage||{})};
   if(flash)S.session._flash=true;
-  localStorage.setItem('hermes-webui-session',S.session.session_id);
+  try{localStorage.setItem('hermes-webui-session',S.session.session_id);}catch(_){}
   _setActiveSessionUrl(S.session.session_id);
   _setSessionViewedCount(S.session.session_id, S.session.message_count || 0);
   // Sync chat-header dropdown to the session's model so the UI reflects
@@ -526,7 +526,7 @@ async function loadSession(sid){
   if(typeof syncTopbar==='function') syncTopbar();
   _setSessionViewedCount(S.session.session_id, Number(data.session.message_count || 0));
   _clearSessionCompletionUnread(S.session.session_id);
-  localStorage.setItem('hermes-webui-session',S.session.session_id);
+  try{localStorage.setItem('hermes-webui-session',S.session.session_id);}catch(_){}
   _setActiveSessionUrl(S.session.session_id);
 
   const activeStreamId=S.session.active_stream_id||null;

tests/test_issue2386_localstorage_quota.py

@@ -0,0 +1,34 @@
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def _script(path):
+    return (ROOT / path).read_text()
+
+
+def _assert_storage_setitem_guarded(src, needle):
+    matches = [line.strip() for line in src.splitlines() if needle in line]
+    assert matches, f"expected at least one {needle} write"
+    for line in matches:
+        assert line.startswith("try{localStorage.setItem("), (
+            f"localStorage quota errors must not escape from {needle} writes: {line}"
+        )
+        assert "catch(_)" in line or "catch(e)" in line or "catch{}" in line
+
+
+def test_active_session_localstorage_writes_ignore_quota_errors():
+    """Session persistence writes are best-effort when the browser quota is full (#2386)."""
+    for path in ["static/sessions.js", "static/commands.js", "static/messages.js"]:
+        _assert_storage_setitem_guarded(
+            _script(path),
+            "localStorage.setItem('hermes-webui-session'",
+        )
+
+
+def test_workspace_panel_localstorage_write_ignores_quota_errors():
+    """Workspace panel state should not break UI toggles if localStorage throws (#2386)."""
+    _assert_storage_setitem_guarded(
+        _script("static/boot.js"),
+        "localStorage.setItem('hermes-webui-workspace-panel'",
+    )